Vaporizing combustion chamber for a heater running on liquid fuel

ABSTRACT

A vaporizing combustion chamber for a heater running on liquid fuel, in particular a vehicle heater, in which inter alia two pipes disposed concentrically one inside the other form therebetween an annular chamber which is closed at a first end. At the second end, the annular chamber is open and leads into a flame diaphragm which projects radially inwards from the outer pipe and is located at a spacing in front of the inner pipe. At both its ends the inner pipe is substantially open and the opening at the second end is contracted by a concentric baffle edge of a baffle plate. In order to improve the emission values of the combustion chamber exhaust gas and reduce combustion noises both when the combustion chamber is disposed horizontally and when it is disposed vertically, the opening in the flame diaphragm is eccentric to the opening, in the inner pipe, formed by the baffle edge of the baffle plate. The radially larger wall surface of the flame diaphragm is in the vicinity of the fuel-introduction point on the periphery.

The present invention pertains to a vaporizing chamber for a heateroperated with liquid fuel, especially a vehicle heater, according to thepreamble of patent claim 1.

The emission levels of the waste gas of the combustion chamber are poorand disturbing combustion-related noises are generated due to thecircumferential, punctiform admission of the fuel into the fuel-airmixing space of the combustion chamber. This equally applies to thehorizontal and vertical operating positions of the combustion chamber,and in the case of a horizontal operating position, the fuel is usuallyadmitted in an area that is not located under a horizontal planeextending through the axis of the combustion chamber. The point of fueladmission is always vertically at the top in the case of combustionchambers arranged vertically.

The object of the present invention is to eliminate the above-describeddrawbacks. This object is accomplished by a design of the combustionchamber according to the characterizing features of patent claim 1.

Advantageous embodiments are the subject of the subclaims.

The present invention is based on the idea of improving the combustionand consequently the emission and noise behavior of a heater equippedwith a combustion chamber of this class by a clever design and guidanceof the combustion chamber flame into the combustion chamber flame tube.Experiments carried out within the framework of the present inventionrevealed that various eccentric positions of a flame orifice opening ofequal area lead to considerably different emission and noise levels. Themost favorable extent of eccentric arrangement of the opening and itsposition on the circumference can be readily determined experimentallyfor a certain combustion chamber configuration of this class.

Different eccentricities may be optimal depending on whether theoperating position of the combustion chamber is vertical or horizontaland whether the fuel is admitted in the zenith or at the axial height ofthe combustion chamber in the case of a horizontal chamber, or whetherthe fuel is admitted into a vertical chamber. This also applies to thecircumferential position of the center of eccentricity.

If the same combustion chamber is intended for vertical and horizontalinstallation and for different levels of the point of fuel admission inthe case of horizontal installation, the extent of the eccentricity andthe position on the circumference from the center of the eccentricity,which are optimal for predetermined, different operating positions, canbe determined as a compromise by simple experiments.

One exemplary embodiment of the present invention is shown in thedrawings.

In the drawings,

FIG. 1 shows a longitudinal section through a combustion chamber alongline I--I in FIG. 2, and

FIG. 2 shows a view of the combustion chamber according to arrow II inFIG. 1.

The combustion chamber comprises a fuel-air-mixing and ignition spacearea 1 and a flame tube 2 joining downstream of the ignited mixture.

The area 1 is formed by an outer tube 3 and an inner tube 4 locatedconcentrically in same, as well as by a flame orifice 5, by which theflame tube 2 is connected to the area 1.

The annular space located between the outer tube 3 and the inner tube 4is closed at the end located opposite the flame orifice 5. The innerwall of the outer tube 3 is lined with a porous, absorbent body 6.Liquid fuel, e.g., diesel fuel, is admitted into the said absorbent body6 at a point of admission 7 indicated by a dash-dotted circle. Theignition at the start of the burner takes place in the area of thispoint of admission.

The combustion air is fed into the inner tube 4 through the open end ofthe said inner tube 4 that is located opposite the flame orifice 5. Theair flows into the inner tube 4 in a swirling flow. The inner tube 4 isprovided with a baffle plate 8 at its end facing the flame orifice.Directly adjoining the said baffle plate 8, radially open, axial slots9, which extend over about one third of the overall length of the innertube 4, are located in the jacket of the inner tube 4. Due to thecombustion air being admitted as a swirling flow through the inner tube4, the combustion air penetrates into the mixing space area of thecombustion chamber, which extends around the inner tube 4 and is formedessentially by an annular space 10 between the outer and inner tubes 3and 4, through the slots 9, on the one hand, and through the opening ofthe baffle plate 8. The igniting flame is formed in the area between thebaffle plate 8 and the flame orifice 5 during the continuous operationof the burner in order to subsequently develop completely within theflame tube 2.

The opening of the flame orifice 5 is a circular surface arrangedeccentrically to the axis of the combustion chamber. The eccentricoffset of the center of the flame orifice opening is in a direction bywhich the wall area of the flame orifice 5, which joins the point offuel admission 7, is enlarged. This can be clearly seen in FIG. 2. Theposition of the combustion chamber shown in FIG. 2 corresponds to ahorizontal operating position with a point of fuel admission 7 locatedapproximately at the axial level. The center of the opening of the flameorifice is rotated circumferentially vertically downward by about 45° inrelation to the representation in FIG. 2. With such a position of theopening of the flame orifice 5, it was possible to observe a compromisein the experiments carried out with respect to good emission andcombustion noise levels for different installation positions of thecombustion chamber. The operating positions suitable for this are theinstallation position shown in FIG. 2, as well an installation positionin which the point of fuel admission 7 is at the top in the zenith, aswell as a vertical installation position with the flame tube locatedvertically at the bottom.

In the specific example shown, the outer diameter of the flame orificeis about 45 mm, and the diameter of the opening of the flame orifice is20 mm. With a flame orifice 5 of such a size, the eccentricity found tobe optimal is e=2 mm, and the rotation of the center of the orificeopening in relation to a horizontal plane shown in FIG. 2, whichintersects the axis of the combustion chamber, is about at α=45°.

In the case of the combustion chamber according to the example shown,the combustion air is admitted into the inner tube 4 with a swirl in thedirection of arrow D.

We claim:
 1. A vaporizing combustion chamber comprising:an outer tubewith a first and second end; an inner tube positioned concentricallywith said outer tube, said inner tube defining open first and secondends, said inner tube also defining a plurality of slots adjacent saidsecond end of said inner tube, said inner and outer tubes defining anannular space between said inner and outer tubes, said annular spacebeing closed at a first end adjacent said first end of said inner tube,said annular space being open at a second end adjacent said second endof said inner tube; a baffle plate connected to said open second end ofsaid inner tube, said baffle plate defining an axial opening reducing asize of said open second end, said inner tube guiding combustion airfrom said first open end of said inner tube through said inner tube andpartly through said slots and partly through said axial opening; a flameorifice wall extending radially inward from said second end of saidouter tube and spaced from said second end of said inner tube, saidflame orifice wall defining a flame orifice opening positionedeccentrically to said axial opening of said baffle plate, said flameorifice wall having an enlarged radial section; a porous absorbent bodyconnected to an inner surface of said outer tube; fuel admission meansfor admitting fuel to said porous absorbent body in a punctiform mannerat a locally limited point of admission adjacent to said first end ofsaid outer tube and said radially enlarged section of said flame orificewall; a flame tube positioned adjacent said flame orifice wall forreceiving a flame from said flame orifice opening.
 2. A vaporizingcombustion chamber in accordance with claim 1, wherein:said second endof said inner tube and said flame orifice wall define a radial gap; saidinner tube guiding the combustion air in a swirled pattern through saidinner tube.
 3. A vaporizing combustion chamber in accordance with claim1, wherein:a radial distance is formed between an edge of said flameorifice opening and an outer edge of said second end of said inner tubedue to said flame orifice opening being positioned eccentrically, saidradial distance having a direction angularly spaced up to substantially45 degrees from a line including said point of fuel admission and anaxis of the combustion chamber in a plane extending at right angles tosaid axis of the combustion chamber.
 4. A vaporizing combustion chamberin accordance with claim 3, wherein:a minimum radial distance betweensaid edge of said flame orifice opening and said outer edge at saidsecond end of said inner tube is substantially zero.
 5. A vaporizingcombustion chamber in accordance with claim 1, wherein:a minimum radialdistance between an edge of said flame orifice opening and an outercircumference at said second end of said inner tube is substantiallyzero.
 6. A vaporizing combustion chamber in accordance with claim 1,wherein:a maximum radial distance is formed between an edge of saidflame orifice opening and an edge of said axial opening due to saidflame orifice opening being positioned eccentrically to said axialopening, said maximum radial distance having a direction angularlyspaced less than substantially 45 degrees from a line including saidpoint of fuel admission and an axis of said inner tube.
 7. A vaporizingcombustion chamber in accordance with claim 6, wherein:said angularspacing is in a plane extending at right angles to said axis of saidinner tube.
 8. A vaporizing combustion chamber in accordance with claim6, wherein:a length of a minimum radial distance between said edge ofsaid flame orifice opening and said edge of said axial opening issubstantially zero.
 9. A vaporizing combustion chamber in accordancewith claim 1, wherein:a length of a minimum radial distance formedbetween an edge of said flame orifice opening and an edge of said axialopening due to said flame orifice opening being positioned eccentricallyto said axial opening is substantially zero.